Portable battery pack



FIG. 1 is a perspective view of a portable battery pack showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a perspective view thereof when in a use holding an electronic device.

The broken lines of FIGS. 6 and 8 are for showing environmental features and are not part of the design. 

CLAIM The ornamental design for a portable battery pack, as shown and described. 